TRD format

From SinclairFAQ
Jump to: navigation, search

TRD Disk Image Format

The TRD format was created for storing Betadisk/TR-DOS disk images for emulation. The Russian Spectrum clones (Pentagon Scorpion) use the TR-DOS disk operating system with builtin Beta Disk interface.

This format is member of the Easy Disk Image Formats and contains only the data of sectors.

TRD file structure

TRD images can store single or double sided 40 or 80 track disk images.

File Header

There is no any header or file signature (magic bytes).


Sectors laid from 1st to last within a track:

  • Sector 1
  • Sector 2


  • Sector last

Tracks follow the “alt” schema:

  • Side: 0 Track: 0
  • Side: 1 Track: 0
  • Side: 0 Track: 1


  • Side: 0 Track: 79
  • Side: 1 Track: 79

File length

TR-DOS uses 256 BPS and 16 SPT for disks, so a

  • 40 track 1 sided image length is 163840 byte (1×40×16×256)
  • 40 track 2 sided image length is 327680 byte
  • 80 track 1 sided image length is 327680 byte
  • 80 track 2 sided image length is 655360 byte

Partial images

TRD files may end before the calculated full length if sectors up to the end contains no data.

e.g. Prince of Persia - PRINCE_P.TRD (2 sided 80 track disk image) is only 255488 bytes length, because the last sector which contains data is h0t31s6 (2×31×16+6)×256

SCL Format

SCL format is an alternative storage format for TR-DOS files. Instead of a TRD image, SCL stores only the directory structure and data of files.

External Links

TR-DOS info from RAMSOFT